9051 Background: Patients with stage IV metastatic melanoma are usually felt to be incurable with a median survival of 6.4 months and a 5-year survival of only 2%. Biochemotherapy has shown promise with long-term survival in selected patients. We felt the study of prognostic factors would determine which patients might benefit the most from this intensive therapy. Methods: 135 consecutive patients with stage IV melanoma treated with decrescendo biochemotherapy followed by maintenance immunotherapy at one melanoma treatment center were studied to determine the most important prognostic factors; these factors were then validated by analysis of 133 patients treated in a multi-center trial at other institutions. Patients were treated using the inpatient regimen of O'Day (JCO23:710s,2005 abstract). Results: Median overall survival (OS) was 16.6 months with 1-year survival of 70% and 5-year survival of 28%. Median progression-free survival (PFS) was 7.6 months with 15% progression-free at 5 years. PFS curves showed no relapses after 30 months, so remissions were durable. For OS performance status 0, normal LDH, stage M1a, and non-visceral sites of metastases were favorable prognostic factors. For PFS performance status 0, normal LDH, female sex, age <50 and stage M1a were favorable prognostic factors Multivariate analysis demonstrated two important prognostic factors for survival: normal serum LDH and the presence of either skin or nodes as one of the sites of metastatic disease. The group with normal LDH and skin or node metastases had a relatively good prognosis with median survival of 44 months and a 5-year survival of 38%. Conversely patients with elevated LDH without any skin or nodal metastases had a poor prognosis, with no long-term survivors. Conclusions: Metastatic melanoma patients treated with biochemotherapy and maintenance immunotherapy that have either a normal LDH or skin or nodes as one of their metastatic sites may have durable remissions of their disease, and this therapy should be studied further in these groups. [Table: see text]